Muffler with spiral conical insert



y 15, 1951 L. F. BALTZER 2,552,615

MUFFLER WITH SPIRAL CONICAL INSERT Filed May 29, 1948 2 Sheets-Sheet lInventor F BALTZER Attorney.

y 1951 L. F. sA'L'rzER 2,552,615

MUFFLER WITH SPIRAL CONICAL INSERT Filed May 29, 1948 2 Sheets-Sheet 2Inventor LAWRENCE F BALTZER by I Patented May 15, 1951 MUFFLER WITHSPIRAL CONICAL INSERT Lawrence F. Baltzer, Berwick, Nova Scotia, CanadaApplication May 29, 1948, Serial No. 29,969

'7 Claims.

This invention relates to improvements in a muffler with spiral conicalinsert for automobile engines and the like and appertains particularlyto a silencing device to mufiie or deaden the noise of the exhaust gasesof internal combustion motors by smoothing out the sharp intermittentimpulses.

An object of the invention is to provide a muffler casing with a spiralroll, preferably formed of a corrugated ribbon and displacedlongitudinally into a cone, filling the casing for the full diameterthereof to provide a maximum of longitudinally extending passages andsurfaces to cause a frictional flow-retarding influence on thecontacting and immediately adjacent portions of the current of gases andby thus setting up a differ ential in the speed of flow, as between theportion of gases actually or nearly contacting the surfaces and thatportion midway between the flow-slowing surfaces, stretch out the sharpreports into a smooth, evenly flowing, quiet stream.

A further object of the invention is to provide an exhaust mufi'ler withample cross sectional area and wherein the insert affords directlongitudinal passage from inlet to outlet so that though the flowimpulses are evened out no back pressure ever develops.

A still further object of the invention is to provide a mufiier of thenature and for the purposes specified that is characterized bystructural simplicity, durability and efficiency and being capable ofmanufacture at reasonable cost is thereb rendered commerciallydesirable.

To the accomplishment of these and related objects as shall becomeapparent as the description proceeds, the invention resides in theconstruction, combination and arrangement of parts as shall behereinafter more fully described, illustrated in the accompanyingdrawings, and pointed out in the claims hereunto appended.

The invention will be best understood and can be more clearly describedwhen reference is had to the drawings forming a part of this disclosurewherein like characters indicate like parts throughout the severalviews.

In the drawings:

Figure 1 is a longitudinal section through a mufiier casing showing myimproved silencing elements arranged therein;

Figure 2 is a similar sectional view showing a modified arrangement ofthe silencing elements;

Figure 3 is another such sectional view with a further modified form ofsilencing insert;

Figure 4 is an enlarged cross-section of a muffier casing with aspirally rolled metal ribbon insert in elevation; and

Figures 5 and 6 are perspective views of alternative forms of metalribbon with the corrugations thereof extending diagonally andtransversely respectively; and

Figure '7 is a perspective of another insert.

In carrying out this invention I have found a simple and economical wayto form a flow equalizing and silencing insert for a muffler shell is toroll a narrow strip or ribbon of metal into a reasonably tight spiralwith a diameter substantially equal to the interior of the casing so asto fit snugly therein. Four such spiral rolls I will be seen in anelongated cylindrical muffler shell or casing 2 with inlet and outletopenings 3 and 4 at opposite ends thereof, in the form shown inFigure 1. The diameter of the shell should be not less thanapproximately three times that of the ports.

The spiral ribbon silencing inserts i may be of smooth material but Iprefer to form them of corrugated metal strip 5, with the corrugationsrunning diagonally or at an angle to the length of ribbon as seen inFigure 5 or transversely as seen in Figure 6.

An effective treatment of these closely wound spirals I is to displacethe center of the coil longitudinally, pulling the roll out into coneshape as in Figures 1 and 2. These cones can then be arranged in manyways, e. g., in pairs as in Figure l, with the apex of one nestingwithin the base of the other, one such pair in each end of the casingand the apexes of the inner or center most cone of each pair nearlymeeting midway of the muffler casing; in Figure 2, a nesged pair ofcones I are located about the center of the casing, both facing withtheir apexes to the outlet and illustrated to indicate the corrugations5 on the ribbon of the cone to the right as diagonal and the othertransverse; and a very simple form appears in Figure 3 where thesilencer insert I is a closely wound spiral roll of a substantiallywider corrugated ribbon, that is not distorted into conical for-m.

Normally the spiral roll of corrugated metal ribbon is wound tightlyenough that it will not rattle or vibrate and no extraneous fasteners orsupports are necessary. However, when a plain metal strip is used or amore openly wound spiral is desired in the roll, a spreader may be usedsuch as the diametrical bar 6, appearing in Figure 4, with spacing teeth1 extendin between adjacent convolutions of the spiral coil or the teethmay be integral lugs out-struck from the coil material itself to be selfspacing even 3 as the corrugations of the preferred ribbon material.

Following is the theory advanced for the effective sound muflling actionof this device: As the stream of exhaust gases enter the muffler by theinlet 3, the intermittent and spaced high pressure spots in the flow onexpanding to occupy the greater space afforded tend to be reduced inintensity and when thus thinned down pass through the multitude of smallcommon direction establishing passages in the coiled ribbon coneimproving uniformity of pressure and flow over the cross-sectional areaof the muffier. Here too the sum-total extent of the passage areasurface stretches out the pressure spots further with the accompanyinglevelling influence. In a set-up as shown in Figure 1 where the streamof exhaust gases is subjected to this treatment on four successiveoccasions in its passage through the muffler and still no appreciableback pressure developed because of the reasonably unimpeded direct-lineflow, a satisfactory degree of silencing is obtained, thestraight-through current keeps the inserts clean so they last longergiving top performance and there are no baffles to burn out or workloose and rattle.

The use of a coil of corrugated ribbon also breaks up the gas flow intoa great many similar and parallel jets, each so small as to be almostinaudible and each subject to expansion on emerging from the passageway:Where the corrugations are diagonal, a multitude of tiny parallel andspiralling jets are set up that can be straightened out to parallel theaxis of the muffler by a cone of transverse corrugated ribbon or made tospiral in the opposite direction by a reversed arrangement of thediagonal corrugations in a succeedingly placed ribbon cone insert.

From the foregoing description taken in connection with the accompanyingdrawings, it will be manifest that a muffler is provided that willfulfil all the necessary requirements of such a device, but as manychanges could be made in the above description and many apparentlywidely different embodiments of the invention may be constructed withinthe scope of the appended claims, without departing from the spirit orscope thereof, it is intended that all matters contained in the saidaccompanying specification and drawings shall be interpreted asillustrative and not in a limitative or restrictive sense.

Having thus described my invention, what I claim as new and desire tosecure by Letters Patent is:

1. An exhaust muffler comprising a cylindrical casing with inlet anddischarge openings at pposite ends and a transversely disposed closelywound spiral roll of metal ribbon of uniform width filling the interiordiameter thereof, said roll being displaced longitudinally into conicalform.

2. An exhaust mufiier comprising a cylindrical casing with inlet anddischarge openings at opposite ends and a closely rolled spiral cone ofcorrugated metal ribbon filling the entire crosssectional area of saidcasing and providing a multitude of parallel, longitudinally extendingpassages of very small cross section.

3. An exhaust muffler comprising a cylindrical casing with inlet anddischarge openings at opposite ends and a closely rolled spiral cone ofcorrugated metal ribbon filling the entire cross-sectional rear of saidcasing and providing a multitude of tiny passages and 0f considerablelength affording a maximum of flow-paralleling area for a given distancewithout creating back pressure.

An exhaust muffler comprising a cylindrical casing with the usual inletand discharge opening, and a tightly wound roll of corrugated ribbon ofuniform width of a diameter to fit snugly in said cylinder disposedtransversely therein between said openings, said corrugated ribbon rollproviding a multitude of tiny parallel passages and being displacedlongitudinally into conical form.

5. Ihe combination with the structure set forth in claim 4 wherein atleast one o1 said corrugated ribbon rolls has the corrugations extendingtransversel of the length of ribbon.

6. The combination with the structure set forth in claim 4 wherein atleast one of said corrugated ribbon rolls has the corrugations extendingdiagonally of the length of ribbon.

7. The combination with the structure set forth in claim 4 wherein atleast two or more of said rolls are of conical form, the centre of therolls being displaced longitudinally, and at least partially nested onewithin the other.

LAWRENCE F. BALTZER.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,685,701 Blanchard Sept. 25,1928 1,897,649 Good Feb. 14, 1933 2,033,784 Pougher Mar. 10, 19362,075,316 Tyden Mar. 30, 1937 2,274,599 Freeman Feb. 24, 1942 FOREIGNPATENTS Number Country Date 1,332 Great Britain Nov. 6, 1913 89,289Sweden May 19, 1937

